High throughput continuous pulsed laser deposition process and apparatus

ABSTRACT

The present invention relates to an apparatus and method for forming a high-temperature superconducting film on a long tape substrate at speeds suitable for large-scale production. The method includes a spooling system for use in a high-throughput, continuous pulsed laser deposition (PLD) process in which a superconducting layer, such as yttrium-barium-copper-oxide (YBCO), is deposited atop a buffered metal substrate tape that is translated through one or more deposition chambers via the action of a reel-to-reel spooling system and a conductive-radiant multi-zone substrate heater. It also optionally includes a multi-target manipulator apparatus and multiple laser beams in which multiple targets are impinged upon simultaneously.

FIELD OF THE INVENTION

The present invention relates to an apparatus and method for forming ahigh-temperature superconducting film on a long tape substrate at speedssuitable for large-scale production, includes a spooling system for usein a high-throughput, continuous pulsed laser deposition (PLD) process.

BACKGROUND OF THE INVENTION

In the past three decades, electricity has risen from 25% to 40% ofend-use energy consumption in the United States. With this rising demandfor power comes an increasingly critical requirement for highlyreliable, high quality power. As power demands continue to grow, olderurban electric power systems in particular are being pushed to the limitof performance, requiring new solutions.

Wire forms the basic building block of the world's electric powersystem, including transformers, transmission and distribution systems,and motors. The discovery of revolutionary high-temperaturesuperconductor (HTS) compounds in 1986 led to the development of aradically new type of wire for the power industry; this discovery is themost fundamental advance in wire technology in more than a century.

HTS wire offers best-in-class performance, carrying over one hundredtimes more current than do conventional copper and aluminum conductorsof the same physical dimension. The superior power density of HTS wirewill enable a new generation of power industry technologies. It offersmajor size, weight, and efficiency benefits. HTS technologies will drivedown costs and increase the capacity and reliability of electric powersystems in a variety of ways. For example, HTS wire is capable oftransmitting two to five times more power through existing rights ofway.

This new cable will offer a powerful tool to improve the performance ofpower grids while reducing their environmental footprint. However, todate only short lengths of coated conductor wire samples have beenfabricated at high performance levels with any of the conventionalfabrication processes.

In order for HTS technology to become commercially viable for use in thepower generation and distribution industry, it will be necessary todevelop techniques for continuous, high-throughput production of HTStape. Several challenges must be overcome in order to enable thecost-effective production of long lengths (i.e., several kilometers) ofHTS-coated conductor wire.

Vapor deposition is a process for manufacturing HTS tape in which vaporsof superconducting material such as YBCO are deposited on a tape-likelength of buffered metal substrate, thereby forming an HTS coating onthe tape substrate. Well-known vapor deposition processes includephysical vapor deposition (PVD), chemical vapor deposition (CVD), andpulsed laser deposition (PLD). PLD has shown great promise for thedeposition of superconducting thin films, due in large part to itsoperational simplicity, its flexibility in vacuum requirements, and thecongruent, stoichiometric transfer of material that results from thegeneration of a highly forward-directed plume from target to substrate.

In a pulsed laser deposition (PLD) process in which a laser is used toevaporate a material, where atoms of the material subsequently coat asurface that is exposed to the evaporated material, thereby forming afilm on that surface. PLD is a process suitable for manufacturing HTSwires with high current-carrying capacity. In this case, a targetcomprising a stoichiometric chemical composition of the desired layer isablated by a pulsing laser, forming a plume of ablated material to whicha buffered substrate is exposed, thereby coating the buffered substratewith the desired material and forming a coated wire or tape. Using a PLDprocess it is possible to deposit a superconducting layer atop atranslating flexible buffered polycrystalline metal tape in acontinuous, assembly line manufacturing process. However, to date onlyshort lengths of coated conductor wire samples have been fabricated athigh performance levels using prior art vapor deposition processes andequipment.

The manufacture of long lengths of HTS tapes via a PLD processnecessitates a system that provides for the translation of the tapesthrough a deposition chamber where they receive the desired thin filmcoating Youm, U.S. Pat. No. 6,147,033, dated Nov. 14, 2000, and entitled“Apparatus And Method For Forming A Film On A Tape Substrate,” providesa tape transport system particularly well suited for translating asubstrate tape through a deposition chamber.

As described by Youm, the superconducting film is deposited on the tapesubstrate wound around a cylindrical substrate holder inserted in anauxiliary chamber housed completely within a main deposition chamber.The cylindrical substrate holder rotates during the whole depositionprocess. Vapors of film materials are supplied from the main chamberthrough an opening between the two chambers. According to Youm, it ispossible to form HTS film rapidly onto a tape substrate having a lengthup to 300 meters. While this represents a step toward the large-scaleproduction of HTS coated tape, it is limited in its scalability. Toachieve significantly longer lengths of HTS coated tape the cylindricalsubstrate holder must increase in size accordingly, making itimpractical to be housed within the main vapor deposition chamber. Thus,a drawback of the vapor deposition process described in Youm is that thesystem is not easily scalable to produce long lengths (e.g, severalkilometers) of HTS coated tape and is therefore not suited for thelarge-scale production of HTS coated wire.

Several other challenges must be overcome in order to enable thecost-effective production of long lengths (i.e., several kilometers) ofHTS coated conductor wire.

A first challenge to the continuous deposition of HTS tapes utilizing areel-to-reel tape transport system that is not overcome by Youm is themaintenance optimum tape tension throughout the extended deposition runsnecessary to high-throughput systems. If the correct level of tautnessis not maintained, the tape sags. This results in a variation in thetarget-to-substrate distance and a compromise of the thin filmuniformity.

A second technical challenge to the continuous deposition of HTS tapesutilizing a reel-to-reel tape transport system that is not overcome byYoum is the maintenance of the tape at the optimal speed throughoutextended deposition runs. As the spools rotate and the tape istranslated through a chamber, the tape must remain at the same positionwithin the deposition zone, regardless of the radii of tape housed oneach spool. Lateral, as well as longitudinal, movement of the taperesults in an inconsistent and non-uniform deposition resulting invariations in film thickness. The importance of film uniformity cannotbe an overemphasized: if there is an insufficient superconductingquality at a single point over the entire length of a few hundred metersof tape, the current carrying capacity of the entire length of tape iscompromised. Further, any elements that serve to position the tape mustdo so in such a way as to not induce stress or strain in the tape, whichmay damage the delicate thin films

Another technical challenge not overcome by Youm is how to wind the tapeonto a spool subsequent to its undergoing the deposition process withoutdamaging the delicate thin film housed thereon. The ceramic grains ofsuperconducting films may fracture if bent beyond a certain strain,which may result in a decrease in the critical current-carrying capacityof the finished superconductor tape.

To achieve the proper bonding of the evaporated material to thesubstrate during a typical PVD, CVD, or PLD process it is necessary toheat the substrate. Thus, a substrate heater that is capable ofsustaining the substrate at a process temperature ranging typically from500 to 1500° C. is required. Current PVD, CVD, or PI) processestypically employ a stationary substrate mounted on a stationarysubstrate holder, where the substrate holder incorporates a heatingelement. Since the substrate is in direct contact with the heatedsubstrate holder, heating of the substrate takes place by conduction.

An example of a conventional stationary substrate heater is disclosed inChen et al., U.S. Pat. No. 6,066,836, dated May 23, 2000 and entitled“Sigh temperature resistive heater for a process chamber”. Chen et al.describes a structure for a processing apparatus such as a chemicalvapor deposition chamber that includes a resistively heated substrateholder including a support surface that includes an additional resistiveheating element. The heated substrate holder is disk-shaped toaccommodate a substrate, such as a wafer, in a semiconductorapplication. Chen's substrate heater includes a heating element thatprovides a single heating zone, that is, one uniform temperature ismaintained across the entire substrate

However, in the case of a continuously translating substrate as isnecessary for a continuous flow manufacturing process, it is difficultto maintain a uniform temperature profile using resistive heaters asdisclosed by the prior art. Any local loss of contact with the heatingelement by a rapidly moving substrate can cause large temperaturevariations and in turn inhomogeneities in the coating film.Consequently, a technical challenge to overcome is how to heat a rapidlymoving substrate in a continuous flow high-throughput manufacturingprocess for producing long lengths of HTS-coated wire.

In the case of a translating substrate in a continuous flowmanufacturing process, multiple temperature zones having differenttemperature requirements, such as a preheating zone, a deposition zone,and a cooling zone, are desirable. Current substrate heaters do notprovide multiple heating zones with differing temperature ranges asrequired for continuous flow manufacturing of HTS-coated wire and thusare not suited for use in the large-scale production of HTS-coated wire.

In the PLD process, a film is deposited on a substrate by the action ofa laser beam impinging on a target material that is located in closeproximity to the substrate, thereby creating a plume of ablated material(plasma) to which the substrate is exposed. Conventional PLD systemsutilize a single laser beam that impinges on a target mounted on atarget manipulator. The target manipulator provides an appropriatetarget rotation and oscillation. In a particular well-known example,multi-target manipulators may hold multiple targets for sequential usein a PLD process. In this case, as the material of any given target isconsumed during the PLD process, the multi-target manipulator indexesfrom one target to the next. However, in the large-scale continuousproduction of HTS-coated wire, a multi-laser beam PLD process, in whichmultiple laser beams impinge on multiple targets simultaneously, may beused, thereby simultaneously creating multiple overlapping plumes towhich a translating substrate is exposed. In this way, the depositionregion is expanded in length, thereby improving the overall throughputof the PLD process compared with a single laser/single target PLDprocess. Conventional target manipulators are therefore of limited usein a multi-laser beam PLD application.

An example of a conventional target manipulator is described in Kim etal., U.S. Pat. No. 5,942,040, entitled “Multi-Target Manipulator ForPulsed Laser Deposition Apparatus.” Kim et al. discloses a multi-targetmanipulator for a pulsed laser deposition apparatus, including a drivingmechanism that includes a stepping motor and a motion feed for providingrotation to the target disk driving shaft and the target driving motorshaft. The driving mechanism further includes a driving transmission andhead-supporting member that transmits a rotational motion for rotatingthe target disk and the target so as to locate a target material on thefocal point of the laser beam.

Although Kim et al provides a multi-target manipulator, the multipletargets are arranged on a circular disk with the intent of being indexedfrom one to another for consumption one at a time. Although it isconceivable that multiple lasers could be focused on all targetssimultaneously, it is not practical for a continuous flow application inwhich a substrate tape is translating in a straight line, therebyrequiring the targets to be arranged in a straight line. A furtherlimitation is that Kim et al.'s the multi-target manipulator providesrotation to only one target at a time. This type of multi-targetmanipulator is therefore not suited for use in the large-scaleproduction of HTS-coated wire utilizing a continuously translatingsubstrate through a deposition chamber.

It is conceivable that several target manipulators, such as Kim et al.'smulti-target manipulator, could be used in combination with multiplelaser beams arranged sequentially in a straight line along the path ofthe translating substrate tape. However, using such an arrangement ofseveral conventional target manipulators in a multi-laser beam PLDsystem is very costly and therefore not practical. Also, conventionaltarget manipulators occupy lot of space and as a result, there will belarge gaps between targets. This will result in large gaps betweenplumes from the targets when used with multiple lasers. Consequently,this arrangement of several conventional target manipulators is noteconomically or practically suited for use in the large-scale productionof HTS-coated wire.

It is therefore an object of the invention to provide a tape transportsystem well suited to the continuous high-throughput manufacture of HTStapes.

It is another object of the invention to provide a tape transport systemthat maintains optimum tape tension throughout extended deposition runs.

It is yet another object of the invention to provide a tape transportsystem that maintains tapes at an optimal target-to-substrate distancethroughout extended deposition runs.

It is yet another object of the invention to provide a tape transportsystem that prevents damage to the newly deposited superconducting filmsas the tape winds onto a take-up spool.

It is an object of the invention to provide a substrate heater for usewith a non-stationary substrate in a continuous flow vapor depositionprocess.

It is another object of the invention to provide a substrate heater withmultiple independent heating zones for use with a non-stationarysubstrate in a continuous flow vapor deposition process.

It is yet another object of the invention to provide a substrate heaterthat achieves the desired heating of a translating substrate by acombination of conductive and radiative heating during a continuous flowvapor deposition process.

It is an object of the invention to provide a multi-target manipulatorthat provides multiple targets arranged in line for simultaneous use ina multi-laser beam PLD process for the large-scale production ofHTS-coated wire.

It is yet another object of the invention to cost-effectively provide amulti-target manipulator for use in a multi-laser beam PLD process forthe large-scale production of HTS-coated wire.

It is an object of the present invention to provide a PLD apparatus andmethod for forming highly uniform HTS film on a tape substrate.

BRIEF SUMMARY OF THE PRESENT INVENTION

The present invention is a PLD system and method for use in thelarge-scale, high-throughput production of HTS coated wire. Inparticular, the present invention includes a high-throughput PLDmanufacturing system that provides continuous production of HTS coatedtape via the deposition of, for example, yttrium-barium-copper-oxide(YBa₂Cu₃O₇ or “YBCO”) film onto a buffered metal substrate.

In its simplest form, the PLD system of the present invention includes amain deposition chamber disposed between a first and second vacuumchamber. The PLD system further includes a controlled reel-to-reelspooling system capable of translating buffered metal substrate tapethrough the multiple chambers. The spooling system includes a payoutspool disposed within the first vacuum chamber for feeding the substratetape into the deposition chamber and a take-up spool disposed within thesecond vacuum chamber for receiving the HTS-coated wire. The size of thedeposition chamber is unaffected by the size of the spools which isvariable depending on the length of the substrate tape wound thereon.

The main deposition chamber further includes elements that allow theformation of a deposition zone that is longer than those in conventionaldeposition systems without sacrificing the uniformity of deposition ofthe coating material on the substrate. Such elements include multiplelaser beams, which impinge simultaneously upon multiple targets mountedon a multi-target manipulator, thereby simultaneously forming multipleplumes of HTS particles, to which the substrate is exposed in adeposition zone.

The presence of multiple overlapping plumes arranged sequentiallyeffectively lengthens the deposition zone wherein the substrate isexposed to the evaporant material. The thickness of the HTS filmdeposited onto the substrate tape is controlled by the rotational speedof a payout and take-up spool within the spooling system, therebycontrolling the time that the substrate is present in the depositionzone.

The reel-to-reel tape transport system includes a pair of spools drivenby a pair of identical motors that force the rotation and thereby thetranslation of a substrate tape at a rate of between 10 and 500 metersper hour through one or more adjacent deposition chambers in which alayer of superconducting material, such as YBCO, is deposited. Themotors are managed by a controller such that, as one motor drives thespools, the other imparts an amount of resistance sufficient to providean optimal tension in the tape. A pair of idlers maintains the tape atan optimal position as it translates through a deposition zone. Theidlers come into contact with the non-coated side of the tape as thetape winds off a payout spool and onto a take-up spool; the idlers shiftin their positioning so as to accommodate the changing radii of tapehoused on each spool.

Subsequent to undergoing the deposition of a superconducting layer, thetape is made to wind onto a take-up spool such that the HTS-coated sidewinds in an orientation toward the center of the spool rather thantoward the outer perimeter of the spool, as the superconducting film isless likely to be damaged when under compressive strain rather than whenunder tensile strain. As an additional protective measure, a length ofpolymer interleaf may be wound into the take-up spool between tapelayers as the tape winds onto the take-up spool, thereby protecting thesuperconducting layer form being scratched by the non-coated side of thesubstrate tape.

The system also includes a scalable multi-zone substrate heater forheating by a combination of conduction and radiation a continuouslytranslating substrate in a high-throughput continuous production vapordeposition process. The multi-zone substrate heater of the presentinvention is suitable for use inside a vapor deposition chamber fordepositing, for example, a HTS film on a buffered metal substrate tapetranslating through the deposition chamber.

In order to optimally reach the desired temperature profile across theentire length of a deposition zone within the deposition chamber, themulti-zone heater embodiment of the present invention includes anarrangement of heating elements that provides multiple temperaturezones. Such temperature zones include, for example, a preheating zoneproviding a maximum temperature of 860° C., a deposition heating zoneproviding a maximum temperature of 900° C., and a cooling zone providinga maximum temperature of 860° C., where the preheating zone is orientedtoward the entry point of the vapor deposition zone and the cooling zoneis oriented toward the exit point of the vapor deposition zone.

In another embodiment of the invention, a plurality of depositionheating zones are arranged sequentially between the preheating zone andthe cooling zone in a scalable fashion to accommodate process depositionzones of varying length depending on the size of the deposition chamberand/or the desired throughput.

For use in a pulsed laser deposition (PLD) process, the multi-zoneheater of the present invention includes passages that enable one ormore laser beams to pass unimpeded to one or more targets, whichotherwise would be obstructed by the size of such a substrate heaterthat is necessary to accommodate the increased deposition zone lengthnecessary to a high throughput PLD system. The multi-zone heater alsoallows for accurate monitoring of the substrate temperature viathermocouples and an optical pathway disposed through its structure thatenables a pyrometer to make temperature measurements to the non-coatedside of the translating tape.

The system also optionally includes a multi-target manipulatorapparatus. The multi-target manipulator apparatus includes a pluralityof target manipulators mechanically coupled to one another in a line viaa bar or platen. Each target manipulator within the multi-targetmanipulator apparatus includes a target holder driven by an independentdrive motor that provides rotational motion to the target holder via ashaft Furthermore, the bar or platen connecting the plurality of targetmanipulators one to another is mechanically coupled to a commonvariable-speed actuator that provides the oscillatory motion incombination with the rotational motion provided by the respectivemotors.

In operation, the multi-target manipulator apparatus, having multipletarget holders upon which are placed multiple targets, respectively,allows multiple laser beams to impinge simultaneously upon the targets.As a result, multiple plumes of ablated material, to which a substrateis exposed for a predetermined time, are formed, thereby forming a filmon the substrate. Furthermore, due to the appropriate spacing betweenthe multiple target manipulators arranged in a line, the resultingplumes slightly overlap one to another and therefore ensure uniformityof film deposition over an expanded deposition zone length.

The multi-target manipulator apparatus of the present invention isespecially suitable for use in a multi-laser beam PLD process for thelarge-scale production of HTS-coated wire.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a front view of the pulsed laser deposition systemof the present invention, in its simplest form, for forming HTS coatedtape.

FIG. 1B illustrates a front view of a typical deposition system housinga spooling system in accordance with the invention.

FIG. 2A illustrates a cross-sectional view of the pulsed laserdeposition system of the present invention in operation, taken alongline AA of FIG. 1.

FIG. 2B illustrates a top view of a broad representation of amulti-laser beam PLD system to which the multi-target manipulatorapparatus of the present invention is suited.

FIG. 2C illustrates a side view of the multi-laser beam PLD system.

FIGS. 2D, 2E, and 2F illustrate the target impingement geometries thatare the result of various actions of a conventional target manipulator.

FIG. 3 illustrates a side view of a multi-zone substrate heater in itssimplest form for use in a vapor deposition process for formingHTS-coated wire.

FIG. 4 illustrates an end view of the multi-zone substrate heater ofFIG. 3.

FIGS. 5A and 5B illustrate a top and side view, respectively, of a firstembodiment of the multi-target manipulator apparatus of the presentinvention.

FIGS. 6A and 6B illustrate a top and side view, respectively, of asecond embodiment of the multi-target manipulator apparatus of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1A and 1B are front views of a PLD system 100 of the presentinvention in its simplest form. The PLD system 100 includes a maindeposition chamber 102 arranged between a first vacuum chamber 104 and asecond vacuum chamber 106, where a chamber wall 116 having an opening117 provides separation and isolation between the deposition chamber 102and the vacuum chamber 104, and where a chamber wall 118 having anopening 119 provides separation and isolation between the vacuum chamber106 and the deposition chamber 102. Furthermore, enclosing thedeposition chamber 102, the vacuum chamber 104, and the vacuum chamber106 collectively is a chamber enclosure 120. The openings 117 and 119provide a passageway through which a translating substrate may travelfrom one chamber to the next.

The deposition chamber 102 is a chamber designed specifically for pulsedlaser deposition applications, such as a 12-or 18-inch vacuum chambercommercially available by Neocera, although those skilled in the artwill appreciate that a number of alternative vendors manufacture vacuumchambers in a variety of shapes and sizes that may be implemented as thedeposition chamber 102 of the present invention. The surrounding vacuumchambers 104 and 106 may be of a variety of dimensions and serve in thepresent invention to house elements of the spooling system.

Housed within the deposition chamber 102 are one or more targetmanipulators, for example, a target manipulator 122 that includes amotor 123 and a target holder 124 mechanically connected via a shaft125. The target holder 124 is a mount onto which a target 136 composedof HTS material, such as YBCO or cerium oxide (CeO₂), depending upon theapplication, is placed. The target 136 is available commercially fromsuppliers such as Target Materials, Praxair, and SuperconductiveComponents. In its simplest form, the target manipulator 122 may be oneof many off-the-shelf models available to the industry that enablestranslation and rotation (rastering) of the target 136 and/or targetindexing (target selection in multiple target holders) in such a way asto ensure a uniform wearing away of the target 136 during the PLDprocess and to prevent surface irregularities or undesirablemicrostructures from developing on the target 136 due to repeatedablation events in localized regions.

Alternatively, to provide maximum throughput, the target manipulator 122is a multi-target manipulator apparatus suitable to handle multipleinstantiations of the target 136 for use in a multi-laser PLD process.In this case, the multi-target manipulator is useful in a multiple orsplit laser beam PLD system having a single or multi-zone substrateheater. This multi-target manipulator suitably provides the requiredrotating and variable-speed side-to-side oscillating motion to multipleinstantiations of the target 136 simultaneously each having a laser beamimpinging upon their surface concurrently, thereby maximizing thedeposition zone and thus optimizing the throughput in the continuousproduction PLD process.

Multiple instantiations of the target holder 124 of the targetmanipulator 122 are oriented when installed toward a substrate heater200 that is also housed within the deposition chamber 102. The substrateheater 200 is a heating device used to heat and maintain the temperatureof the substrate to within a range of approximately 750 to 900° C. Inits simplest form, the substrate heater 200 may be a conductive orradiant heater that is available commercially from vendors such asThermionics, Thermocoax, Neocera, and PVD Products. However, for thepurpose of continuous, long tape deposition, a heater with combinedconductive and radiative heat transfer is preferred in order to achieveoptimum substrate temperature as the substrate moves through thedeposition zone. Alternatively, to provide maximum throughput, thesubstrate heater 200 is a multi-zone heater. Such a multi-zone heaterincludes multiple independently controlled and monitored temperaturezones (e.g., a preheating zone providing a maximum temperature of 860°C., one or more deposition heating zones each providing a maximumtemperature of 900° C., and a cooling zone providing a maximumtemperature of 860° C.) arranged sequentially along the axis of the tapetranslation in order to optimally reach the desired temperatures acrossthe entire length of an expanded deposition zone made possible by theuse of a target manipulator 122 suitable to handle multipleinstantiations of the target 136 in combination with a multiple or splitlaser beam PLD system.

Furthermore, in a preferred embodiment, the substrate heater 200 is ascalable multi-zone heater design that includes multiple “depositionheating zones” arranged sequentially along the axis of the tapetranslation to accommodate process deposition zones of varying lengthwithin deposition chamber 102.

The design of the multi-zone heater allows multiple laser beams to passunobstructed to multiple instantiations of the target 136 and allows foraccurate monitoring of the substrate temperature via thermocouplesthroughout the continuous PLD process.

As shown in more detail in FIG. 1B, housed within the deposition system100 is the spooling system 120 in accordance with the invention. Thespooling system 120 includes a payout spool 128, upon which a substratetape 140 is wound, having an associated drive motor 124 with anassociated controller 126, all housed in the chamber 104 along with anidler 130. The spooling system 120 further includes a take-up spool 132,onto which the substrate tape 140 in the form of HTS-coated tape iswound, having an associated drive motor 133 with an associatedcontroller 135, all housed in the chamber 106 along with an idler 134.The substrate tape 140 laces through the deposition system 100 from thepayout spool 128 and then rides on the idler 130 through a opening 117in the chamber wall 116, and thus passes into the main depositionchamber 102. Once inside the deposition chamber 102, the substrate tape140 subsequently passes through a deposition zone and then exits thedeposition chamber 102 via an opening 119 in the chamber wall 118, andpasses into the chamber 106. The non-coated side of the substrate tape140 subsequently rides on the idler 134 prior to being wound onto thetake-up spool 132. The idlers 130 and 134 ensure stable positioning ofthe substrate tape and also ensure that the proper amount of tension ismaintained on the substrate tape, thereby preventing the development ofslack. The dimensions of the deposition zone are defined by a target136, a plume 146, and a substrate heater (not shown). The plume 146 is aplasma cloud resulting from the material of the target 136 melting andsubsequently evaporating explosively when impinged upon by a laser beamas is well known in a PLD process.

FIGS. 1A and 1B show the spooling system lacing through a singledeposition chamber 102 as one example. However, the spooling system mayspan a plurality of adjacent chambers.

The payout spool 128 is a reel onto which an extended length of thesubstrate tape 140 is wound. A typical diameter of the payout spool 128is eight inches. The payout spool 128 may contain a protective interleafmaterial wound between the layers of the substrate tape 142 containedthereon for protective purposes. The take-up spool 130 is a reel ontowhich the substrate tape winds after it is exposed to a pulsed laserdeposition process in the deposition chamber 102. A typical diameter ofthe take-up spool 132 is eight inches. If disposed near the depositionzone, the take-up spool 132 and/or the payout spool 128 may be cooled.

The motors 124 and 133 are connected to the payout spool 122 and thetake-up spool 130, respectively. The motors 124 and 133 are identicaland serve one of two functions: one motor serves to drive a spool andtranslate the substrate tape 140 through deposition chamber(s) 102,while the other motor serves to provide a preset amount of tension inthe substrate tape. In FIG. 1 b, the motor 133 is driving the take-upspool 132 and thus translating the substrate tape 140 through thedeposition chamber 102, while the motor 124 is providing a small amountof resistance to the rotation of the payout spool 128, thereby producinga desired amount of tension in translating the substrate tape 140.Certain applications may require the substrate tape 140 to reversethrough the deposition chamber 102, e.g., in the case of in situ postdeposition annealing, in which case the roles of the motor 124 and themotor 133 are reversed. It is for this reason that the motors 124 and132 are identical and capable of serving dual functions.

The controllers 126 and 135 control the action of the motors 124 and132, respectively. The controllers 126 and 135 are responsible formaintaining the translation of the substrate tape 140 through thedeposition chamber(s) 102 at the optimumn speed and proper tension, aswell as ensuring a compact winding of the substrate tape 140 onto thetake-up spool 130. The controllers 126 and 135 may provide real timeinformation about the tension of the tape 140 to an externally locatedcontrol source or, alternately, tension may be actively monitored withthe use of a tension-sensing device such as a load cell (not shown).Such a load cell mechanism may come into contact with the tape 140 andcommunicate actively with the controllers 126 and 135 in a feedbackloop. The controllers 126 and 135 may then compare the communicatedtension with a preset tension value stored within their memories andsubsequently adjust the tension of the tape 140 via control of the motor124 and/or 133.

The idlers 130 and 134 are rotating elements that are in contact withthe non-coated side of the substrate tape 140. A typical diameter of theidlers 130 and 134 is between three and five inches. The idlers 128 and136 maintain the translating substrate tape 140 at a consistentorientation within the deposition zone. The idlers 128 and 136 preventmovement of the substrate tape 142 in any direction except for that ofits translation, ensuring the substrate tape 140 is exposed to anoptimum portion of the plume 142. A precise distance from the plume 142(typically two inches) must be maintained to ensure a uniform andconsistent deposition of material onto the substrate tape 140.Additionally, it is likely that there may be additional pairs of idlersincluded in applications in which the spooling system 120 translates thesubstrate tape 142 through more than one adjacent deposition chambers.The idlers 128 and 136 additionally allow for adjustment in thepositioning of the substrate tape 140, as is desirable when it isdetermined that the substrate-to-target 144 distance must change.

In operation, the payout spool 122 containing the substrate tape 140,which has been exposed to a buffer deposition process such as IBAD, isreceived from the buffer layer deposition processing area and is mountedin the payout spool 122 location of the spooling system 120. The take-upspool 130 is similarly mounted, and a leader section of tape attached tothe take-up spool 130 is laced under the idler 136, through the slit119, in some cases through a multi-zone substrate heater, through theslit 138, and under the idler 128, and is spot-welded or spliced to thesubstrate tape 140. The heater is turned on, the motor 132 and the motor124 are engaged, the substrate tape 140 translates through thedeposition chamber 102 at a constant rate of between 10 and 500 metersper hour, and a PLD process occurs that deposits a superconducting layeratop the substrate tape 140.

During translation of the substrate tape 142 (from left to right, asseen in FIG. 1 b), the motor 132 drives the take-up spool 130 and causesthe substrate tape 140 to translate through the deposition chamber 102.The motor 124 provides a small amount of resistance to the rotation ofthe payout spool 122 and thereby produces the desired amount of tensionin the translating the substrate tape 142. The controller 126 and thecontroller 135 regulate the actions of the motor 124 and the motor 132,respectively, ensuring that the motors 124 and 133 translate thesubstrate tape 142 through the deposition chamber 102 at a constantspeed and optimum tension. The tension may be monitored actively by thecontrollers 126 and 135 or by a tension-sensing device such as a loadcell that is in communication with the controllers 126 and 135. Themotor 124 and the motor 133 are identical and are capable of translatingthe substrate tape 140 through the deposition chamber 102 in reverse, ascertain applications such as post-deposition in situ annealing demandsuch features. Additionally, the motor 124 and the motor 133 may includetension-controlling devices such as clutches that control the torqueimparted to the take-up spool 132 and the payout spool 128. Suchclutches are elements well known to the art. The idlers 128 and 136maintain the translating substrate tape 142 at a constant height throughthe deposition chamber 102, ensuring an optimum substrate depositiontemperature as the substrate tape 140 translates through or near asubstrate heating element, as well as ensuring a uniform and consistentdeposition of material onto the substrate tape 140 by maintaining theoptimum substrate-to-target 136 distance (typically two inches).Additionally, the idlers 130 and 134 help to prevent any lateral motionor the formation of twists in translating substrate tape 140.

The substrate tape 140 winds onto the take-up spool 132 such that theHTS-coated side of the substrate tape 140 is oriented toward the centerof the take-up spool 132. The ceramic film deposited on the substratetape 140 is less likely to be damaged when under compressive stress thanwhen under tensile stress, as the ceramic grains atop the substrate tape140 may fracture when bent beyond a certain strain, resulting in adecrease in the critical current-carrying capacity of the finishedsuperconductor tape. As an additional protective measure, a length ofpolymer interleaf may be wound into the take-up spool 132 between layersas the substrate tape 140 winds onto the take-up spool 132, protectingthe superconducting layer of the substrate tape 140 from being scratchedby the non-coated side of the substrate tape 140. Polymer interleaflayers may also be included in the payout spool 128 and collected by acollector spool as the substrate tape 140 rolls off the payout spool128. Additionally, the substrate tape 140 may undergo silver sputteringin a chamber adjacent to the deposition chamber 102 before winding ontothe take-up spool 132 to provide a protective coating to the substratetape 140.

The substrate tape 140 is an extended length of buffered substrate thatmay have dimensions of one centimeter in width and upwards of onehundred meters in length. An example of the substrate 140 is a bufferedmetal (e.g., polycrystalline nickel alloy) tape. In the case of abuffered metal tape, the substrate 140 is composed of, for example,Hastelloy, Inconel, or stainless steel that has been cleaned andpolished and measures, for example, between 25 and 100 microns inthickness, with, for example, a yttria-stabilized zirconia (YSZ), ceriumoxide (CeO₂) or magnesium oxide (MgO) buffer layer deposited thereon byone of several well-known deposition techniques, such as ion beamassisted deposition (IBAD). Optionally, the substrate 140 may include“dummy tape,” or a length of non-processed substrate, at both ends toallow easier lacing through the multi-laser beam PLD system 100 andeasier subsequent handling.

FIG. 2A shows a cross-sectional view of the PLD system 100 in operation,taken along line AA of FIG. 1A. As shown in FIG. 2A, it is evident thatthe PLD system 100 of the present invention further includes a laser 142such as a Lambda Physik model STEEL 670 Excimer laser, characterized bystabilized average power of 200 watt and a pulse repetition rate up to300 Hz. Those skilled in the art, however, will readily perceive that avariety of lasers may enable the practice of this present invention.

In operation, the laser 142 emits a pulsed laser beam 210 thatsubsequently passes through a commercially available adjustable focusoptical lens 144 and then reflects off a mirror 146 that is alight-reflecting surface available commercially from suppliers such asRoper Scientific. The PLD system 100 includes a laser port 148 that hasa quartz window through which the laser beam 210 enters into thedeposition chamber 102. Because a laser beam, such as the laser beam210, is operating continuously during the PLD process, contaminateparticles of the target material may tend to cloud the laser windowwithin the laser port 148 over time. Thus, in the preferred embodiment,the laser port 148 includes a laser beam delivery system that monitorsand automatically maintains a laser beam 210 of constant energy bymonitoring the intensity of the laser beam 210 via sensors and feedingback to a controller such that the laser 142 power level may be adjustedup or down accordingly.

A plume 212 is a plasma cloud resulting from the material of the target136 melting and subsequently evaporating explosively when impinged uponby the laser beam 210.

The PLD system 100 further includes various controls and monitoringdevices, such as a mass flow controller (MFC) 150 that regulates themass of gas that enters the deposition chamber 102; a vacuum pump 152mounted to the deposition chamber 102 via a pump port 154 in chamberwall 120, where the vacuum pump 152 may be a combination of a mechanicalpump and a turbo-molecular pump and functions to assist in controllingthe pressure inside the deposition chamber 102 and purging gas from thedeposition chamber 102, and where the pump port 154 also acts as theoutlet through which gas is purged from the deposition chamber 102; apressure gauge 156 that is a pressure-sensing device, such as acapacitance monometer, a hot cathode, a cold cathode, a convectron, or anumber of other applicable instruments; and an electron gun 158 thatduring operation emits an electron stream 214 into the depositionchamber 102 and onto the deposited HTS layers of the substrate 140 at agrazing angle less than five degrees. The electron stream 214 impingeson the layers deposited on the substrate 140 and is diffracted andanalyzed at a RHEED pattern analysis area 160. The RHEED patternanalysis area 160 is an analysis area at which a diffraction pattern isproduced due to the interaction of the incident electron stream 214 andthe crystalline arrangement of the surface of film deposited onto thesubstrate 140. RHEED diffraction patterns, often represented by an Ewaldsphere, are produced when the momentum of incident electron stream 214and that of the diffracted electron beam differ by a reciprocal latticevector of the deposition surface, and are used to monitor the growth,crystallinity, and crystal orientation of the film (layers depositedonto the substrate 140) in situ. Additionally, other in situ monitoringtools that may be incorporated into the PLD system 100 include a heliumneon (HeNe) laser with a HeNe pass filter and photodiode, an X-raydiffractometer system, or an X-ray fluorescence system.

With continued reference to FIGS. 1A and 2A, the operation of the PLDsystem 100 in its simplest form (i.e., one laser beam 210 impinging onone target 136 forming one plume 212) is as follows. The payout spool128, on which is wound a length of substrate 140 that is coated with abuffer layer as received from the buffer processing area, is mountedwithin the vacuum chamber 104. The substrate 140 is laced through theopenings 117 and 119 in the chamber walls 116 and 118, respectively, andonto the take-up spool 132 in vacuum chamber 106, all the while being incontact with the idlers 130 and 134 to prevent any slack from developingin the length of the substrate 140. Additionally, the idlers 130 and 134are set such that the substrate 140 is a predetermined distance from thetarget 136. A typical distance of the substrate 140 from the target 136is approximately two inches.

The target 136 is mounted to the target holder 124 within the vacuumenvironment of the deposition chamber 102 in close proximity to thesubstrate 140, onto which the evaporant material, such as YBCO, is to bedeposited.

The vacuum environment of the deposition chamber 102 is developed by thevacuum pump 152 and monitored by the pressure gauge 156. Oxygen ispumped into the deposition chamber 102 via the MFC 150.

The substrate 140 is heated to an optimal deposition temperature between500 and 900° C., preferably between about 750 and about 830° C., by theradiant substrate heater 200. The pulsed laser beam 210, which isgenerated by the laser 142 located outside the deposition chamber 102,is focused by the lens 144, reflects off the nirror 146, and is directedinto the deposition chamber 102 through the laser port 148 to impingeupon a portion of the target 136, causing the formation of the plume212, which emanates from that portion of the target 136 radiated by thelaser beam 210 toward the substrate 140 in a highly forward-directedfashion. The particles contained in the plume 212 are thus depositedonto the surface of the substrate 140 as the tape translates through thedeposition chamber 102 at a predetermined speed controlled by therotational speed of the take-up spool 132.

The target 136 is rastered, or rotated and translated, by the targetmanipulator 122 during the laser impingement events to preventundesirable microstructures (cones) from developing on the surface ofthe target 136 and, further, to assure an even wearing away of thetarget 136. As the HTS coated tape formed by the PLD process exits thedeposition chamber 102 through the opening 119 in the chamber wall 118,it may optionally undergo silver sputtering in an adjacent chamber toprovide a protective coating. Alternately, a protective film may windonto the take-up spool 132 as the superconducting tape winds onto thetake-up spool 132 to provide a protective barrier.

As the deposition process occurs, the in situ monitoring tools asdescribed in FIG. 2A are used to monitor the growth, crystallinity,crystal orientation, and thickness of the film being deposited onto thesubstrate 140.

The deposition chamber 102 may additionally include several extra portsfor user diagnostics or other applications, including, but not limitedto, target and substrate view ports, ports for atomic absorption oremission spectroscopy, and a pair of ports for in situ ellipsometry.

To provide a PLD system 100 that is highly optimized for the continuous,high throughput production of HTS wire, the translation rate of thesubstrate 140 through the PLD system 100 is increased by expanding thelength of the deposition zone in the following manner. In an alternativeembodiment that achieves an expanded length deposition zone, the PLDsystem 100 of the present invention includes multiple instantiations ofthe laser beam 210 for impinging upon multiple instantiations of thetarget 136 arranged sequentially along the axis of the tape translation,thereby forming multiple instantiations of the plume 212 simultaneouslyto which the substrate 140 is exposed. The multiple instantiations ofthe target 136 are mounted onto the target manipulator 122 that suitablydesigned to handle the multiple instantiations of the target 136. Themultiple instantiations of the plume 212 are arranged sequentially alongthe axis of the tape translation and are slightly overlapping, therebyforming an expanded length deposition zone wherein the substrate 140 isexposed to the evaporant material. Furthermore, this expanded depositionzone provides a film deposition uniformity within ±5%. The thickness ofthe HTS film deposited onto the substrate 140 is controlled by therotational speed of the take-up spool 132, thereby controlling the timethat the substrate 140 is present in the deposition zone.

Multiple instantiations of the laser beam 210 may be supplied bymultiple instantiations of the laser 142, respectively, or by a singlelaser 142 having a laser output that is split into multipleinstantiations of the laser beam 210 by optical devices that performwell-known laser splitting functions. In this case, the intensity of thelaser beam from the laser 142 is sufficiently powerful, when split, tosupply the energy to multiple instantiations of the laser beam 210required for a PLD process.

With continued reference to FIGS. 1A and 2A, the operation of thisalternative embodiment of the PLD system 100 (i.e., multipleinstantiations of the laser beam 210 impinging on multipleinstantiations of the target 136 forming multiple instantiations of theplume 212 simultaneously) is as follows. The substrate 140 is lacedthrough the deposition chamber 102 from the payout spool 128 to thetake-up spool 132 as described previously. The idlers 130 and 134 areset such that the substrate 140 is a predetermined distance from themultiple instantiations of the target 136. A typical distance of thesubstrate 140 from the targets 136 is approximately five centimeters[two inches].

Multiple instantiations of the target 136 are mounted to multipleinstantiations of the target holder 124, respectively, of the targetmanipulator 122 within the vacuum environment of the deposition chamber102 in close proximity to the substrate 140, onto which the evaporantmaterial, such as YBCO, is to be deposited. The substrate 140 is heatedby convection to an optimal deposition temperature between 500 and 900°C., preferably between about 750 and about 830° C., by the substrateheater 200 that in this embodiment is a radiant multi-zone substrateheater. Multiple instantiations of the pulsed laser beam 210 are focusedby multiple instantiations of the lens 144, reflecting off multipleinstantiations of the mirror 146, and are directed into the depositionchamber 102 through the multiple instantiations of the laser port 148.The target manipulator 122 suitably provides the required rotating andvariable-speed side-to-side oscillating motion to multipleinstantiations of the target 136 simultaneously, each having a laserbeam 210 impinging upon their surface concurrently, causing theformation of multiple instantiations of the plume 212, which overlap andemanate toward the substrate 140, thereby maximizing the deposition zoneand thus optimizing the throughput in the continuous production PLDprocess. The particles produced by multiple instantiations of the plume212 are thereby deposited onto the surface of the substrate 140 as thetape translates through the deposition chamber 102 at a predeterminedspeed controlled by the rotational speed of the take-up spool 132.

Several key observations can be made regarding the multiple laserbeam\target\plume arrangement of the PLD system 100 of the presentinvention:

For a given HTS film thickness, an increase in throughput is achievedthat is directly proportional to the number of laser beams and targetsoperating simultaneously (i.e., thereby forming multiple plumes), ascompared with a single laser beam system (i.e., a single plume).

Alternatively, for a given substrate translation speed, an increase inHTS film thickness is achieved that is directly proportional to thenumber of laser beams and targets operating simultaneously (i.e.,thereby forming multiple plumes), as compared with a single laser beamsystem (i.e., a single plume).

High throughput is achieved without sacrificing the uniformity of thedeposited material.

FIG. 3 illustrates a side view of a multi-zone heater 250 in accordancewith the invention, in its simplest form, for use in a vapor depositionprocess for forming HTS-coated wire. Additionally, FIG. 4 illustrates anend view of the multi-zone heater 250 of FIG. 3.

With references to FIGS. 3 and 4, the multi-zone heater 250 of thepresent invention includes a heater block 210 that forms the main bodyof the multi-zone heater 250. A first heating zone formed within theheater block 210 is a preheating zone 212 having a radiant heatingelement 214, such as a lamp, fed by a power feed 216. The power feed 216is electrically connected to an external controller (not shown) forcontrolling the power level of the heating element 214 and therebycontrol its temperature based on feedback to the external controller viaa conventional thermocouple 118 that provides temperature measurementsfirm within the preheating zone 212. The heating element 214 within thepreheating zone 212 is typically capable of providing a maximumtemperature of 860° C.

A second heating zone formed within the heater block 210 is a depositionzone 220 having a radiant heating element 222, such as a lamp, fed by apower feed 124. The power feed 124 is electrically connected to theexternal controller for controlling the power level of the heatingelement 222 and thereby control its temperature based on feedback to theexternal controller via a conventional thermocouple 226 that providestemperature measurements from within the deposition zone 220. Theheating element 222 within the deposition zone 220 is typically capableof providing a maximum temperature of 900° C.

Lastly, a third heating zone formed within the heater block 210 is acooling zone 228 likewise having a radiant heating element 230, such asa lamp, or a resistive heating element such as molybdenum disilicide orsilicon carbide or nickel-iron alloys such as Kanthal, fed by a powerfeed 232. The power feed 232 is likewise electrically connected to theexternal controller for controlling the power level of the heatingelement 230 and thereby control its temperature based on feedback to theexternal controller via a conventional thermocouple 234 that providestemperature measurements from within the cooling zone 228. The heatingelement 230 within the cooling zone 228 is typically capable ofproviding a maximum temperature of 860° C.

A partition 236 provides the physical and thermal boundary between thepreheating zone 212 and the deposition zone 220. Likewise, a partition238 provides the physical and thermal boundary between the depositionzone 220 and the cooling zone 228. The length of the preheating zone212, the deposition zone 220, and the cooling zone 228 each measurestypically between 6.25 and 7.5 cm [2.5 and 3.0 inches]. Alternatively,the length of each zone can be changed by rearranging the thermalelement connection according to requirements. In operation, the maximumΔT between the preheating zone 212 and the deposition zone 220, andbetween the cooling zone 228 and the deposition zone 220 is typically200° C., and the overall temperature stability of the heating zones is±5° C.

A shelf 240 forms the base of the multi-zone heater 200. Disposed withinthe shelf 240 is an aperture 242 that is positioned within thedeposition zone 220. More specifically, the aperture 242 is a windowthat during the deposition process opens briefly to allow a plume ofablated material to reach a substrate 140 to which the aperture 242 isprecisely aligned as the substrate 140 translates through the depositionzone 220. The substrate 140 is, for example, a buffered metal (e.g.,polycrystalline nickel alloy) tape, depending upon the application.

A susceptor 244 is arranged along the entire length of the multi-zoneheater 200, in contact with which the substrate 140 translates in closeproximity to the heating elements 214, 222, and 230. The susceptor 244provides a support for the substrate 140 as it travels through thedeposition zone. The main role of the susceptor 244 is to provide a goodheat transfer to the substrate 140 so as to maintain a uniformtemperature profile in the deposition zone. The susceptor 244 istypically as long as the heater itself and wide enough to cover theentire deposition zone. The thickness of the susceptor 244 is between 5mm and 35 mm, preferably between 10 mm and 20 nm The susceptor 244 isformed of a material, such as hastelloy or inconel or silicon carbide,that can conduct heat as well as transfer infrared radiation from theheating elements 214, 222, and 230 to the substrate 140. The susceptor244 must be capable of withstanding the operating temperatures of thedeposition process. To enable good thermal conduction, the susceptor ismanufactured with a large radius of approximately 5 to 10 m. This radiusenables the tape to be taut against the susceptor. The susceptor isthermally stable so that it does not deform when exposed to the hightemperatures. Any deformation will prevent good contact between thesubstrate and the susceptor. Lastly, the susceptor 244 prevents theplume from contacting the inner components of the multi-zone heater 200.

A coolant chamber 246 formed within the heater block 210 providescontainment for a coolant, such as water, to flow within the heaterblock 210. The coolant is necessary to prevent thermal diffusion fromthe multi-zone heater 200 to other elements within the depositionchamber. The coolant enters the coolant chamber 246 via a plurality ofcoolant inlets 248 and exits via a plurality of coolant outlets 250.

The multi-zone heater 200 is suitable to operate inside a depositionchamber, such as a PLD chamber, and thus is secured within the chambervia a plurality of standoffs 252. Lastly, and with reference to FIG. 4,several free space paths within the multi-zone heater 200 are providedto either the target 136 or the substrate 140. More specifically, achannel 254 provides a free space optical path for an external pulsedlaser beam directed at the target 136 during the deposition process. Therequired incident angle of the laser onto the target 136 is typically 45degrees. Multiple slots 256, for example slots 256 a and 256 b, providea free space path to the deposition side of the substrate 140, therebyallowing Fourier Transform Infared (FTIR) spectroscopy analyses of thesubstrate 140 during the deposition process. FTIR measurements yieldinformation about both the temperature of the substrate 140 and thethickness and uniformity of the film being deposited on the substrate140. A channel 258 is a free space path for the sensing mechanism of apyrometer (not shown), a non-contact temperature-sensing device formonitoring the temperature of the non-deposition side of the substrate140.

With continued reference to FIGS. 3 and 4, the operation of themulti-zone heater 200 in its simplest form is as follows. The multi-zoneheater 200 is mounted within a deposition chamber, such as a PLDchamber, in such a way that the preheating zone 212 is oriented towardthe entry point of the vapor deposition chamber and, conversely, thecooling zone 228 is oriented toward the exit point of the vapordeposition chamber. The substrate 140 is fed into the depositionchamber, passing through the heater block 210 of the multi-zone heater200 of the present invention via the cavity formed by the shield 244.

The temperature of the preheating zone 212 is set typically to between750 and 830° C. via the element 214 under the control of the externalcontroller connecting to the power feed 216. The temperature of thedeposition zone 220 is set typically to about 850° C. via the element222 under the control of the external controller connecting to the powerfeed 124. Lastly, the temperature of the cooling zone 228 is settypically to between 750 and 830° C. via the element 230 under thecontrol of the external controller connecting to the power feed 232.Thermocouples 218, 226, and 234 are placed in holes drilled in the bodyof the susceptor 244 itself and provide continuous temperaturemeasurement feedback to the external controller such that the powerlevel of the elements 214, 222, and 230, respectively, may be adjustedupon the detection of any temperature fluctuations during the depositionprocess, thereby maintaining the desired temperature within each zone.By placing the thermocouples in body of the susceptor, a bettertemperature stability can be maintained.

The substrate 140 translates along the length of the multi-zone heater200 in a flow direction from the preheating zone 212 to the depositionzone 220 and finally exiting through the cooling zone 228. The tensionand translation speed of the substrate 140 are maintained in acontrolled fashion to achieve proper film uniformity and thickness.

The preheating zone 212 raises the temperature of the substrate 140 tobetween 750 and 830° C., preparing it for the deposition zone 220. Onceinside the deposition zone 220, the temperature of the substrate 140rises further to about 850° C. and a film of HTS material is depositedonto the substrate 140 via exposure to a plume of HTS material.

The plume of HTS material is generated by a pulsed laser beam impingingon the surface of the HTS target 136 via channel 254 where the plume ofHTS material enters the multi-zone heater 200 via the aperture 242 thatis synchronized with the pulsed laser beam impinging on the target 136.Having passed through the deposition zone 220, the translating substrate140 passes into the cooling zone 228 where the temperature is lowered tobetween 750 and 830° C., preparing the substrate 140 to exit thedeposition chamber.

Slots 256 a and 256 b provide unobstructed paths to the depositionsurface of the substrate 140 to accommodate FTIR spectroscopy analysesthroughout the deposition process. The FTIR spectroscopy yieldsinformation about the temperature, the thickness, and the uniformity ofthe film being deposited on the substrate 140. Likewise, the channel 258provides an unobstructed path to the non-deposition surface of thesubstrate 140 so that the pyrometer (not shown) may monitor thetemperature of the non-deposition surface of the substrate 140. Lastly,coolant continuously circulates through the coolant chamber 246 via thecoolant inlets 248 and the coolant outlets 250 and thereby maintains thetemperature of the heater block 210 and associated hardware at anacceptable level to prevent damage due to excessive heating.

Alternatively, it is noted that the multi-zone heater 200 of the presentinvention is not limited to a single preheating zone 212, depositionzone 220, and cooling zone 228, as shown in FIG. 1. The multi-zoneheater 200 of the present invention is scalable to any number ofpreheating zones 212, deposition zones 220, and cooling zones 228. Forexample, to support a high-throughput manufacturing process for thecontinuous flow production of HTS-coated wire, an expanded depositionregion is beneficial. Such an expanded deposition region is, forexample, between about 25 and 65 cm [10 and 25 inches], preferablybetween about 30 and 37.5 cm [12.5 and 15.0 inches] in length. In thisembodiment, the multi-zone heater 200 is a scalable multi-zone heaterdesign that includes multiple deposition zones 220 arranged sequentiallyto accommodate process deposition regions of varying length within adeposition chamber, where the deposition chamber has multiple targets136 with multiple laser beams impinging simultaneously on theirrespective surfaces, thereby exposing the substrate 140 to multipleoverlapping plumes of HTS material simultaneously along the length ofthis expanded deposition region via multiple apertures 242.

FIGS. 2B and 2C illustrate a top view and side view, respectively, of anembodiment of the present invention utilizing a multi-laser beam PLDsystem in conjunction with the multi-target manipulator apparatus of thepresent invention. A multi-laser PLD system 300 broadly represents theoperation of a multi-laser beam PLD system. Although FIGS. 2B and 2Cillustrate a multi-laser PLD application, the system is also suited foruse with a split laser beam PLD system.

FIGS. 2B and 2C illustrate the multi-laser PLD system 300, whichincludes a plurality of lasers 142 (e.g., a laser 142 a, a laser 142 b,and a laser 142 c) producing a plurality of laser beams 210 (e.g., alaser beam 210 a, a laser beam 210 b, and a laser beam 210 c),respectively, that pass through a chamber wall 316 via windows andstrike a plurality of targets 136 (e.g., a target 136 a, a target 136 b,and a target 136 c), respectively, at an angle within a PLD chamber. Thelasers 142 are, for example, Lambda Physik model LPX 308i lasers,characterized by a medium to high duty cycle with a pulse repetitionrate up to 100 Hz. Alternative examples of the lasers 142 are LambdaPhysik model STEEL 670 or STEEL 1000 Excimer lasers, capable of pulserepetition rates up to 350 Hz.

In the case of a PLD system for continuous production of HTS-coatedtape, the targets 136 are composed of HTS material, such asyttrium-barium-copper-oxide (YBa₂Cu₃O₇ or “YBCO”) or cerium oxide(CeO₂), depending upon the application. The targets 136 are availablecommercially from suppliers such as Target Materials, Praxair, andSuperconductive Components.

In operation, the lasers 142 a, 142 b, and 142 c producing the laserbeams 210 a, 210 b, and 210 c, respectively, that pass though theirrespective windows in the chamber wall 316 and strike the targets 136 a,136 b, and 136 c, respectively, as illustrated in FIG. 2B. As a result,multiple plumes 212 (e.g., a plume 212 a, a plume 212 b, and a plume 212c) of ablated material (plasma) are formed simultaneously, asillustrated in FIG. 2C. In the example of FIGS. 2B and 2C, the plumes212 a, 212 b, and 212 c are deposited simultaneously on a substrate 140due to the simultaneous action of laser beams 210 a, 21Ob, and 210 cimpinging on the targets 136 a, 136 b, and 136 c, respectively, whichare located in close proximity to the substrate 140, typically aboutfive centimeters [two inches].

The targets 136 a, 136 b, and 136 c are spaced in such a way as toobtain the desired plume overlap, and hence provide a uniform depositionover an expanded length of the substrate 140.

FIGS. 2D, 2E, and 2F illustrate the target impingement geometries thatare the result of various actions of a conventional target manipulator.FIGS. 2D, 2E, and 2F are provided as background and to gain a basicunderstanding of the operation of any state of the art targetmanipulator including a first embodiment of the multi-target manipulatorapparatus of the present invention that is shown in FIGS. 5A and 5B, anda second embodiment of the multi-target manipulator apparatus of thepresent invention that is shown in FIGS. 6A, and 6B.

As well known in the art, target manipulators provide rotational motionas well as side-to-side oscillation. The side-to-side oscillation isprovided with variable speed to optimize the target material usage. Forillustration only, FIGS. 2D, 2E, and 2F incrementally demonstrate eachmotion and the resulting target usage.

With reference to the top and cross-sectional views of FIG. 2D, FIG. 2Dillustrates the target 136 having rotational motion only and a resultingcontinuous circular trench 312 a having sloped walls. The trench 312 ais formed in the target 136 by the action of the laser beam striking thesurface of the target 136. As the target 136 rotates, the sloped wallsof the trench 312 a at a laser impingement area 308 a causes thedirection of the plume 212 to be tilted toward the incoming laser beam210 instead of remaining perpendicular to the surface of the target 136and properly directed toward the substrate 140. The result is that thedeposition process is not uniform or efficient. Additionally, the centerarea of the target 136 remains unused, therefore limiting the time ofoperation. Consequently, a simple rotating target 136, alone, is notacceptable.

With reference to the top and cross-sectional views of FIG. 2E, FIG. 2Eillustrates the target 136 having rotational motion and uniform-speedside-to-side oscillation and a resulting much larger circular laserimpingement area 308 b having sloped walls. A trench 312 b is formed inthe target 136 by the action of the laser beam striking the surface ofthe target 136. The dish-shaped trench 312 b is formed in the target136, where the depth of the dish-shaped trench 312 b is not uniformacross the full diameter of the dish-shaped trench 312 b. Again, thesloped walls of the trench 312 b at the laser impingement area 308 bcauses the direction of the plume 212 to be tilted toward the incominglaser beam instead of remaining perpendicular to the surface of thetarget 136 and properly directed toward the substrate 140. Although thetime of operation is increased because a larger target area is beingutilized, the rotating and uniform-speed side-to-side oscillating motionof the target 136 is still not acceptable.

With reference to the top and cross-sectional views of FIG. 2F, FIG. 2Fillustrates the target 136 having rotational motion and variable speedside-to-side oscillation and a large circular laser impingement area 308c having perpendicular walls. A trench 312 c is formed in the target 136by the action of the laser beam striking the surface of the target 136.The dish-shaped trench 312 c is formed in the target 136, where thedepth of the dish-shaped trench 312 c is uniform across the fulldiameter of the dish-shaped trench 312 c due to the variableside-to-side speed control (i.e., the side-to-side motion is at itshighest speed when the laser beam translates across the center area ofthe target 136 and is at its lowest speed when the laser beam translatesnear the outer radius of the target 136). Consequently, theperpendicular walls of the trench 312 c at the laser impingement area308 c causes the direction of the plume 212 to remain perpendicular tothe surface of the target 136 and properly directed toward the substrate140. Nearly all of the target 136 material is consumed, as compared withthe simple rotating target 136, or the rotating and oscillating withuniform speed target 136. As a result, the combination of the rotatingand variable speed side-to-side oscillating motion of the target 136provides maximum operation time by allowing the maximum amount of target136 material to be used before replacement it needed. The rotating andvariable-speed side-to-side oscillating motion of the target 136 isacceptable.

FIGS. 5A-5B and 6A-6B illustrate additional embodiments, respectively,of a multi-target manipulator in accordance with the invention thatprovides the rotational motion and variable speed side-to-sideoscillation as described in FIG. 2F for multiple targets simultaneouslyin a PLD application.

In a first embodiment, FIGS. 5A and 5B illustrate a top and side view,respectively, of a multi-manipulator assembly 350 of the presentinvention. The multi-manipulator assembly 350 includes a rotatorassembly 310 a, a rotator assembly 310 b, and a rotator assembly 310 c.The rotator assembly 310 a further includes a motor 306 a mechanicallyconnected to a target holder 124 a via a shaft 316 a. The rotatorassembly 310 b further includes a motor 306 b mechanically connected toa target holder 124 b via a shaft 316 b. Likewise, the rotator assembly310 c further includes a motor 306 c mechanically connected to a targetholder 124 c via a shaft 316 c. The rotator assemblies 310 a, 310 b, and310 c are mechanically interconnected by feeding the shafts 316 a, 316b, and 316 c, respectively, through a support bar 318. The shafts 316 a,316 b, and 316 c may be solid shafts that pass through the support bar318 and allowed to rotate via conventional bearing assemblies insertedwithin the support bar 318. Alternatively, the shafts 316 a, 316 b, and316 c may be an assembly where each includes a hollow cylinderconnecting the outer housings of the motors 306 a, 306 b, and 306 c,respectively, to the support bar 318, and where within each hollowcylinder is a rotating shaft passing entirely through the support bar318 and coupling to the target holders 124 a, 124 b, and 124 c.

The multi-manipulator assembly 350 further includes a connection rod 320a and a connection rod 320 b mechanically connected to the support bar318 at opposing ends. The position and orientation of the connectionrods 320 a and 320 b is not limited to that shown in FIG. 5B.Alternative positions and orientations are possible. A variable-speedside-to-side actuator (not shown) is mechanically attached to theconnection rods 320 a and 320 b. The rotator assemblies 310 a, 310 b,and 310 c are suspended from the support bar 318 within the multi-laserPLD system, and are free to move with the action of the variable-speedside-to-side actuator. Furthermore, to provide mechanical stability, themotors 306 a, 306 b, and 306 c are mechanically coupled to one anotherand to the support bar 318 via a bracket 322.

Alternatively, a single motor may be mechanically connected usingconventional methods to all of the three shafts 316 a, 316 b, and 316 c,subsequently driving the target holders 124 a, 124 b, and 124 c,respectively.

The diameter “d” of the target holders 124 a, 124 b, and 124 c istypically less than two inches so as to enable optimum inter-targetspacing and, thus, optimum plume overlap and deposition uniformity. Thespacing “e” between the center points of the target holders 124 a, 124b, and 124 c is set to allow for the optimum plume overlap. The length“l” of the support bar 318 may vary depending on the application andspecific mounting requirements. The width “w” and thickness “t” of thesupport bar 318 are dimensions suitable to accommodate the shafts 316 a,316 b, and 316 c and are also dimensions suitable to provide strength tothe support bar 318 to handle the overall mass of the multi-manipulatorassembly 350.

If the multi-manipulator assembly 350 is located entirely within thedeposition chamber of the multi-laser PLD system when installed, thevariable-speed side-to-side actuator (not shown) and the motors 306 a,306 b, and 306 c are vacuum-compatible. Alternatively, if thevariable-speed side-to-side actuator and the motors 306 a, 306 b, and306 c are located outside of the deposition chamber of the multi-laserPLD system 100 when installed, the support bar 318 and the shafts 316 a,316 b, and 316 c are fed through the chamber wall 316 such that a vacuumseal is maintained and such that the side-to-side motion of themulti-manipulator assembly 350 is still allowed.

In operation, the targets 136 a, 136 b, and 136 c are glued onto thetarget holders 124 a, 124 b, and 124 c, respectively, using a silverpaste, such as Ted Pella. The rotator assemblies 310 a, 310 b, and 310 care activated simultaneously to provide simple rotating motion to thetarget holders 124 a, 124 b, and 124 c, respectively, and subsequentlyto the targets 136 a, 136 b, and 136 c, respectively, via the action ofthe conventional motors 306 a, 306 b, and 306 c, respectively. Thevariable-speed actuator (not shown) attached to the connection rods 320a and 320 b is activated to provide the variable-speed side-to-sideoscillating motion to the target holders 124 a, 124 b, and 124 c.

As a result, the multi-manipulator assembly 350 of the present inventionprovides the rotating and variable-speed side-to-side oscillating motionto the targets 136 a, 136 b, and 136 c, thereby providing optimizedoperation time required in a high-throughput PLD process. Additionally,the use of the multi-manipulator assembly 350 of the present inventionin a PLD process allows a faster film deposition process for a giventhickness or allows for a thicker film deposition for a given PLDprocess speed.

It is important to note that the multi-manipulator assembly 350 of thepresent invention is not limited to three rotator assemblies as shown inFIGS. 5A and 5B. The multi-manipulator assembly 350 of the presentinvention could be implemented with any number of rotator assemblies.

In a second embodiment, FIGS. 6A and 6B illustrate a top and side view,respectively, of a multi-manipulator assembly 400 of the presentinvention. The multi-manipulator assembly 400 is identical to themulti-manipulator assembly 350 of FIGS. 5A and 5B, differing only inthat the rotator assemblies 310 a, 310 b, and 310 c are mounted on asupport plate 410 instead of interconnecting with the support bar 318.As in FIGS. 5A and 5B, a plurality of the connection rods 320 a, 320 b,320 c, and 320 d are mechanically connected to the support plate 410 ateach corner. The position and orientation of the connection rods 320 a,320 b, 320 c, and 320 d is not limited to that shown in FIGS. 6A and 6B.Alternative positions and orientations are possible. As in FIGS. 5A and5B, a variable-speed actuator (not shown) is mechanically attached tothe connection rods 320 a, 320 b, 320 c, and 320 d.

The operation is identical to that of the multi-manipulator assembly 350described in FIGS. 5A and 5B, differing only in that the entireassembly, including the rotator assemblies 310 a, 310 b, and 310 c, aresubjected to the variable-speed side-to-side oscillating motion of theactuator.

If the motors 306 a, 306 b, and 306 c are vacuum-compatible motors, themulti-manipulator assembly 400 is located entirely within themulti-laser PLD system. Alternatively, the motors 306 a, 306 b, and 306c mounted on the support plate 410 are disposed outside of themulti-laser PLD system 100 and the shafts 316 a, 316 b, and 316 c arefed through the chamber wall.

1. A multi-chamber vacuum coating apparatus for coating a substrate tapeutilizing PLD and a reel to reel tape transport system comprising apayout spool chamber containing at least one spool of uncoated substratetape; one or more deposition chambers; a take-up spool chamber capableof accommodating at least one spool of coated substrate tape; whereinthe one or more deposition chambers comprises a substrate heater, amotorized target manipulator, and at least one target mounted on thetarget manipulator where the target manipulator imparts rotary andoscillatory motion to the at least one target; the payout chamber andthe deposition chamber both having an opening therein of sufficientdimension to permit at least one translating tape to be insertedtherethrough; the deposition chamber and the take-up spool chamber bothhaving an opening therein of sufficient dimension to permit at least onesubstrate tape to be inserted there through; the one or more depositionchambers each have the substrate heater and the target manipulatordisposed therein such that the heater and the at least one targetmanipulator define a deposition zone therebetween; and the exterior wallof the apparatus contains openings for at least one laser beam.
 2. Theapparatus of claim 1 wherein there is one deposition chamber.
 3. Theapparatus of claim 1 wherein the heater is a multizone heater.
 4. Themethod of claim 1 wherein the exterior wall of the apparatus containsopenings for multiple laser beams.
 5. The apparatus of claim 1 whereinmultiple targets are mounted on the target manipulator.
 6. The method ofclaim 1 wherein the spool chambers are sized to accommodate from about 2to about 20 spools of substrate tape.
 7. The apparatus of claim 1wherein the spool chambers are sized to accommodate from about 4 toabout 12 spools of substrate tape.
 8. The apparatus of claim 1 whereinthe multizone heater comprises three zones.
 9. The apparatus of claim 1also containing seals in the opening in the chamber walls that maintaina selected pressure differential between the chambers.
 10. A method forthe continuous production of long lengths of HTS coated tape via thedeposition of HTS material onto a translating buffered metal substratetape using utilizing the apparatus of claim 1 comprising the steps of:loading at least one payout spool of buffered substrate tape into apayout spool chamber; lacing the at least one spool of substrate tapefrom the payout chamber through the PLD chamber and into the take upspool chamber, all the while riding on idlers; heating the buffered tapeto a deposition temperature between about 600° C. and about 950° C.;setting the oxygen pressure of the deposition chamber to between about50 and about 1000 mTorr; engaging the motors controlling the payoutspool and the take-up spool to translate the substrate tape through thedeposition chamber; activating the target manipulator; activating the atleast one laser to form at least one laser beam, and focusing the atleast one laser beam to have a laser energy density between one and sixJ/cm² such that multiple instantiations of the laser beam simultaneouslyimpinge on multiple instantiations of the target mounted onto the targetmanipulator, resulting in the creation of multiple instantiations of aplume of vaporized target that slightly overlap; depositing vaporizedtarget onto the translating substrate by translating the substratethrough the deposition zone; and collecting the coated substrate on atthe least one take up spool.
 11. The method of claim 10 wherein thesubstrate heater is a multizone heater.
 12. The method of claim 10wherein at least two laser beams are formed.
 13. The method of claim 10wherein the target manipulator holds multiple targets.
 14. The method ofclaim 10 wherein the spool chambers are sized to accommodate from about2 to about 12 spools of substrate tape.
 15. The method of claim 10wherein there are at least two laser beams and each laser beam isproduced by a different laser.
 16. The method of claim 10 wherein themultizone heater comprises three zones.
 17. The method of claim 10wherein the buffered tape is heated to a deposition temperature betweenabout 750° C. and about 830° C.
 18. The method of claim 10 wherein theoxygen pressure in the deposition chamber is set to about 200 mTorr. 19.The method of claim 16 wherein the multizone heater heats by acombination of conductive and radiative heat transfer.
 20. The method ofclaim 10 wherein the substrate is maintained in contact with a susceptoras it translates through the deposition zone.
 21. The method of claim 20wherein the susceptor which is maintained in contact with the susceptoras it translates through the deposition zone is transversely concavelycurved and has a radius of from about 5 to about 10 meters.